By using an oxide sensing electrode, a stabilized zirconia-based sensor was developed for the selective detection of hydrocarbons at high temperature. Among the 14 kinds of oxides tested, CdO was found to be best suited for the sensing electrode of a tubular device, giving selective and quick response to propylene (C3H6) in air at 600°C. The emf value of the device was almost linear to the logarithm of C3H6 concentration in the range 50-800 ppm. The cross-sensitivities to other gases, such as CH4, C2H4, C2H6, C3H8, H2, CO, NO and NO2, were small or insignificant. Furthermore, a compact planar device, which required no reference gas, was also fabricated. The C3H6 sensitivity of the planar device was found to be hardly influenced by a change in oxygen concentration in the sample gas in the range 2-21 vol.%. A sensing mechanism involving mixed potential was confirmed based on the measurements of polarization curves. (C) 2000 Elsevier Science S.A.
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